Counterbore



fig-3 INVENTOR. asc/m C. HEP/Al.

A TTORNEY.

lll

Patented July 9, 1940 UNiTEo STATES AT1-:NT oFFicE My invention relates to small cutting tools and particularly to counterbores.

An object of my invention is to provide a relatively simple and inexpensive counterbore that shall be highly eilicient in simultaneous chip-cutting and chip-removing actions.

Another object of my invention is to provide a non-clogging heavy-duty counterbore.

Another object of my invention is to provide a counterbore which can be resharpened with a minimum of labor applied to the cutting lips alone, and the operation of which will not be impaired by repeated sharpenings.

Another -object of my invention is to provide a i counterbore having two cutting lips only with uniform chip clearance therebetween over their entire axial length, the cross-sectional shape of the cutting lips being such that they will have uniform strength radially thereof relatively to the cutting stresses to which they will be subjected.

Another object of my invention is to provide a counterbore having two cutting lips only projecting substantially radially from a central stem and extending axially along said central stem at an optimum and constant helix angle, the value of which is such that the amount of chips cut from a piece of work and simultaneously moved away therefrom is substantially the maximum possiblein a counterbore.

Still another object of my invention is to provide a counterbore so designed and constructed that substantially uniform chip-removing action will be effected irrespective of reduction in the axial length of the cutting lips.

Other objects of my invention will either be set l forth in the course of a description of several forms of devices embodying my invention or will be apparent therefrom. The various forms 1 shown in the drawing and described in the specification are those now preferred by me, but it is obvious that all modications coming clearly within the scope of the appended claims are to be considered as part of my invention, which claims are to be limited only by the pertinent prior art.

In the single sheet of drawing:

Figure l is a side elevational view of one form of counterbore embodying my invention,

Fig. 2 is a side elevational view of another form of ccunterbore embodying my invention,

Fig. 3 is a side elevational view of a socket for use with the counterbore shown in 2 of the drawing,

Fig. 4 is a side elevational view of the assembly of the counterbore of Fig. 2 and the socket of Fig. 3, l

Fig. 5 is a view, in end elevation, of the counterbore shown in Fig. 2, and,

Fig. 6 is a View, in end elevation, of'the socket shown in Fig. 3 and taken from the right hand end thereof;

Referring rst to Fig. 1 of the drawing, I have there illustrated a unitary single-piece counterbore il, embodying my invention, and of the design which I now prefer to use for the smaller sizes of counterbore. The device Il includes a rear end portion I3, which may be of substantially circular shape in lateral section and which may be provided with a at l5 intermediate its ends to be engaged by a set screw (not shown). A central stem il is unitary with the portion I3 and coaxial therewith. The external diameter of the stern il may be slightly less than that of the portion i3. forward end of the stem and an annular groove 2l is positioned immediately back of the rear end of the pilot.

A pair of cutting lips 23v project substantially radially from the central stem Il and are positioned in peripheral dia-metrally opposite locations on the central stem. These cutting lips extend in predetermined helical paths axially along the central stem and are integral therewith. The cross-sectional shape of the two cutting lips is uniform throughout their entire axial length and since the cross-section of the central stem is also uniform throughout its length, the clearance between the two cutting lips is constant over their entire length. The shape of the two cutting lips in lateral section is special, as will be hereinafter A pilot I9 is provided at the ,l

more clearly set forth. The depth of the groove 2l is such that its bottom is below the outer diameter of the central stem l'l, which, as has already beeri pointed out is integral with the cutting lips 23. IIhe forward end of each of the cutting lips is ground at a small angle relatively to an axial plane in order to provide a relieved surface, which is ground to obtain efficient Acutting action or" the forward ends of the cutting lips. Referring now to Fig. 2 of the drawing, I have there illustrated a counterbore 25 which, in general, is substantially the same in design and construction as the device shown in Fig. 1 ofthe drawing. The counterbore 25 embodies certain details which I prefer to use in the larger sizes of the device embodying my invention. The device 25 includes a forward pilot 2l, a central stem 29 extending between a groove 3| just back of the pilot 2l to the rear end of the device. A

peripheral, relatively shallow flat groove 33 is provided near the rear end of the stem 29 for a purpose to be set forth hereinafter.` p

A pair of cutting lips 35 project substantially radially from the central stem 29 and are integral therewith, these cutting lips being located in diametrally opposite positions on the central stem and extending in a relatively large, denite and uniform helix angle axially along the central stem. The shape of the cutting lips in lateral section is shown more particularly in Fig. 5 of the drawing, from which it will be seen that the leading face 31 of each cutting lip projects substantially radially outwardly from the surface of the central stem, while the trailing face 4S thereof projects substantially tangentially relatively to the outer peripheral surface of the central stem 29 (Fig. 2). This provides cutting lips which are of substantially uniform strength radially thereof and relatively to the cutting stresses to which the cutting lips will be subjected when in use. 'Ihe forward end face of each of the cutting lips is beveled and ground as has already been described in connection with the device illustrated in Fig. 1 of the drawing.

Referring now to Fig. 3, I have there illustrated a holding and driving socket member 31, the rear end 39 of which may be so shaped as to provide a rotational driving means, one conventional form of which, the well-known Morse taper, is illustrated herewith. The member 31 includes a shank portion 4l having a central bore or axial opening 113 therein, the diameter of this central axial bore being such as to receive, with a relatively close t, the rear end portion 29 of the counterbore 25 shown in Fig. 2i. Any conventional means such as set screw l5 may be provided to extend radially through the outer wall of portion il and into the groove 33 to hold the counterbore E5 in the socket member 31 with an alining interfit. 4

The forward end of socket member 31 is provided with two diametrally opposite helical recesses 41, these recesses being of such shape and dimensions as to form two driving jaws or faces complementary to the trailing faces of the cutting lips 35, thereby providing a driving interflt between the forward axial flanges lill, constituted by the trailing walls of the recesses 41, and the trailing faces of the cutting lips 35. The forward end of member 31 is preferably beveled off as shown at 5l to permit of chips cut by the cutting lips during operation thereof to move axially along not only the counterbore 25 but also, with substantially equal facility, along and past the forward end of the socket member 31.

While I have shown the external diameter of the portion #ii of member 31 as being of substantially the same diameter as the outer diameter of the cutting lips 35, I do not desire to be limited thereto, but may make the diameter of portion dl slightly less than that of the cutting lips 35.

I wish to point out that the external diameter of the central stern should be sufficiently small so that the root diameter of the cutting lips 23 and 35 may be made less than the diameter of the hole which is being counterbored.

I wish to point out here certain details of design and construction wherein my improved counterbore differs from the older types now on the market. I use two cutting lips only, which are of uniform shape in lateral section over their entire length, and which are also of uniform radial depth over their entire axial length, thereby providing uniform and relatively large chip clearance between the cutting lips. 'Ihe cutting lips themselves are relatively thin in lateral section, but are of such shape in lateral section that they have substantially uniform radial strength relatively to the stresses to which they are subjected when in use. I i'lnd it possible to use a greater feeding pressure in operation with my improved ,counterbore than was possible when using the older forms of such devices, thereby effecting the removal of a greater quantity of chips in a given time when working on a given kind of material than was possible heretofore.

While it is desirable to be able to cut or remove large quantities of chips in a given time interval, it is also necessary that these chips be removed from the material being worked on, as fast as they are cut, otherwise the chips would become clogged in the material and the counterbore, necessitating taking out the counterbore and cleaning out the accumulated chips. The relatively large and uniform helix angle of the cutting lips combined with the relatively large and uniform chip clearance therebetween results in removal of the chips from the work as quickly as they are formed, thereby avoiding any clogging action of the chips. This result is obtained irrespective of the axial length of the cutting lips. Resharpening of the cutting faces of the lips is eifected by grinding the forward ends of the cutting lips only, without the removal of any material from any other part of the counterbore.

The helix angle of the cutting lips is such as to have the optimum value for not only effecting cutting of chips but also for effecting movement of the chips awa-y from the work as soon as they are cut. It will be noted that the shape of the forward end of the socket member is such as to provide the least possible obstruction to the movement of chips away from the work, when the twopiece counterbore is used.

'Ihe fit of the rear end portion of the central stem 29 in the axial bore 43 is such as to provide axial alinement of the two members 25 and 21, and a set screw G5 may be provided to hold the two members in proper interfitting relationship. I wish to point out particularly however, that the central stem 29 is not called on to transmit any torsional or driving stresses, in the device shown in Fig. 4 of the drawing. All driving stresses are transmitted to the forward ends of the cutting lips by the cutting lips themselves, by the action of the leading faces i9 on the trailing faces of the cutting lips at the ends thereof which t into the recesses; Il?. It will be evident, because of the helical construction, that the greater the stresses which are being 'transmitted, the greater will be the wedging or interlocking tendency of the cutting lips to interiit with the recesses 41.

I claim as my invention:

i. A unitary counterbore consisting of a central stem having a pilot at its forward end and two diametrally-opposed cutting lips only, projecting in a generally radial direction from said central stem and extending axially thereof back of said pilot at a uniform and relatively large helix angle.

2. A unitary counterbore consisting of a central stem, a pilot at its forward end and two cutting lips only extending at a constant helix angle axially of the central stem with a uniform chip clearance therebetween over their entire axial length, the leading face of said cutting lips extending substantially radially of said central stem and the trailing face of said cutting lips extending substantially tangentially to the su"- face of said central stem.

3. A device as set forth in claim l2 and a holding and driving socket therefor having an alining interflt with said central stem and a driving heiical interiit with said cutting lips.

4. A device as set forth in claim l2 and a holding and driving socket therefor, said socket hava central axial opening in its forward end to receive the rear'end of said central stem and v provided with two recesses at its forward end complementary to said cutting lips to receive the ends thereofand to transmit to the trailing faces thereof the force necessary to drive the counterbore when in use.

5. A device as set forth inclaim 1 and a holding and driving socket therefor having a central alining connection with the central stem and a driving connection with the cutting lips only.

6. A device as set forth in claim 12 and a holding and driving socket therefor, said socket having a central axial opening therein at its forward end to receive the rear end of said central stem, two helical recesses at its forward end complementary to the cutting lips to receive the rear ends thereof to transmit thereto the driving force when in operation, the forward end of said socket being beveled to reduce the resistance to the flow of chips past said forward end of the socket.

7. Acounterbore consisting, of a central stem having two diametrically related spiral cutting lips, the leading or cutting face of each lip being substantially radial with respect to the axis of the counterbore, and the trailing face of each lip being substantially tangent-to the surface of the stem.

8. A counterbore consisting, of a central stem having a pilot at its forward end and having two diametrically related spiral cutting lips which project entirely beyond the outer surface of the central stem, the leading or cutting face Vof each lip being substantially radial with respect to the axis of the counterbore, and the trailing face of each lip being substantially tangent to the surface of the stem, both of the bases of each lip intersecting the outer surface of said central stem and the forward end surface of each lip being beveled at a small angle relative to the axial plane of the stem to provide a relieved surface intersecting the corresponding cutting face.

9. A counterbore consisting, of a central stem having a pilot at its forward end and having two diametrically related spiral cutting lips, theleading or cutting face of each lip being substantially radial with respect to the axis of the counterbore, and the trailing face of each lip being substantially tangent to the surface of the stem.

10. A counterbore consisting, of a central stem having a cylindrical smooth surfaced pilot at its forward end and having two diametrically related spiral cutting lips, the leading or cutting face of each lip being substantially radial with respect to the axis of the counterbore, and the trailing face of each lip being substantially tangent to the surface of the stem, the forward end surface of each lip adjacent the pilot being beveled at a small angle relative to the axial plane of the stem to provide a relieved surface inter-4 of the end of said driving member is substantially equal to the diameter of the stem, said recesses intersecting said bevel, and being diametrically related to the axis of the tool.

12. A counterbore comprising a central stem and only two cutting lips diametrically related at opposite sides of the stem, each lip extending entirely beyond the stem and axially of the stem at a constant helix angle, said lips having their leading and trailing faces intersecting said stem, and the bases of the lips not being substantially greater than one-eighth of the circumference of the stem, whereby chip clearance of approximately three-eighths of the circumference of the stem is had between the lips at opposite sides of the stem.

13. A counterbore comprising a central stern and only two cutting lips diametrically related at opposite sides of the stem, each lip extending entirely beyond the stem and axially of the stem at a constant helix angle of about thirty-three degrees, said lips having their leading and trailing faces intersecting said stem.

14. A counterbore having a central stern and a pilot, and two spiral cutting lips only, said lips being diametrically related at opposite sides of the central stem, and both lying entirely beyond the outer surface of said stem whereby resharpening of the lips in a direction axially and starting from the pilot end of the counterbore may be accomplished throughout the entire axial length of the lips without removal of any material from the central stem.

15. A driving device, for a Acounterboring tool of the type which has a stem and only two spiral cutting lips projecting from and diametrically related to one another at opposite sides of the stem and in which the stem projects axially beyond the lips, comprising a member having a socket for receiving said projecting stem portion and having recesses intersecting said socket, each recess being adapted to receive the end portion of one of said lips, a face of each recess being adapted to assume driving engagement with a corresponding lip, said member having means for releasably holding the tool within the socket against axial motion and with the faces of the recess in driving relation with the end portions of the lips.

16. In combination with a counterboring tool having only two cutting lips diametrically rey lated, each lip having a trailing face, said tool having a stem, part of which projects axially beyond the lips, a driving member having a socket detachably receiving the projecting portion of the stem and having two terminally placed recesses, one receiving an end portion only ofv each lip, and each recess having a leading face in driving relation with the trailing face of the end portion of the corresponding lip, and each socket having a trailing face spaced from the leading face of the end portion of the corresponding lip, and the end of each lip being axially spaced from the bottom of the corresponding recess to provide chip clearance, and means on the driving member and tool cooperable to maintain the aforesaid axially spaced relation of the ends of the lips with reference to` the bottoms of said sockets.

` OSCAR C. I-IEDIN.v 

